Joint for electric cables



2 Sheets-Sheet 1 J. F. WATSON JOINT FOR ELECTRIC CABLES Filed Oct. 29, 1927 'June 5, 1928.

June 5, 1928.

J. F. WATSON are/ 7?) Patented June 5, 1928,

UNITED STATES JOHN FRANCIS WATSON, OF ABBEY WOOD, ENGLAND.

JOINT FOR ELECTRIC CABLES.

Application filed October 29, 1927, Serial No. 229,579, and in Great Britain November 30, 1926.

This invention relates to an improved joint for electric cables. tric cable, particularly one having a core of comparatively large cross-section, difficulty is sometimes experienced owing to the ends of the core showing a tendency to move or creep. This may be due to various causes and may depend to some extent upon the conditions under which the cable is laid, whilst it may naturally in some instances be caused by alteration in the length of the core due to temperature variation-s. From whatever cause it may arise the effect may be a serious disadvantage in practice particularly in the case of super-tension cables which, it jointed in the usual way, may have their efficiency impaired if the movement in question takes place.

This difliculty is overcome according to the present invention by jointing the electric cable in such a manner that its core or cores are in tension, the amount of such tension being preferably regulatable and the arrangement also allowing for any'change of length or position which is likely to take place.

Conveniently the apparatus for the improved joint vcomprises two sockets into which the cores to be joined are secured as, for instance, by sweating, and a spring acting to draw the sockets towards each other and thus keep the cores intension. Good electrical connection between the two sockets is made by means of'wire braid or other suitable flexible conductors.

Preferably the sockets form part of or are attached to telescopic members which tend to be drawn one within the other by a spring.

In one construction according to this invention one socket is attached to a metal tube forming the outer telescopic member and the other socket forms part of or is attached to a central rod or spindle which is screwthreaded for a part of its length and projects into the tube from the other end, thus forming the inner telescopic, member. Between these two members, that is within the outer tube, is a helical spring held in compression between a flange or end plate on the inner end ofthe central rod or spindle and an internal flange at-the opposite end of the outer tube.

On the screwthreaded portion of the inner member is a nut which can be rotated so as After the laying and jointing of an elec-- to draw the inner member more or less out of the outer tube, thus compressing the spring to any desired extent. This nut, when thus rotated, bears against the internal flanged end 01 the outer tube. Electrical connection is made between the socket which is attached to the outer tube and the central rod or spindle by means of flexible copper braid attached to the two members in any suitable way, as by binding with wire and soldering.

In operation the nut is rotated on the screwed portion to compress the spring and withdraw the inner rod to the. desired extent and the two cores to be jointed are then sweated or otherwise secured in their respective sockets. WVhen this has been done the nut is slackened back and the spring then acts to place the two cores in tension.

It will be understood that the jointing ap paratus according to this invention is primarily intended to be placed in a joint box and that the metal tube would be surrounded by tubes or sleeves of insulating material and by insulating compound.

When the improved joint is used for making connections say in a three-core cable, each core would be jointed in the manner described and the three insulating tubes surrounding the joints would be supported within the cast iron or other joint box by suitable insulating supports or spacers, the

whole box being filled with insulating compound in some known way.

In the accompanying drawings,

Figure 1 is a longitudinal sectional view of a joint box for a three-core cable, each core being furnished with a tension joint according to this invention,

Figure 2 is a cross-section on the line 2-2 of Figure 1,

Figure 3 is a longitudinal section drawn to a larger scale showing one of the tension joints with the spring in one extreme operative position Figure 4 is a view similar to Figure 3 with the spring in its other extreme position, and

Figure 5 is an elevation of the tension joint showing the parts in one position which they occupy whilst the joint is being made.

With reference first to Figure 1, A is a joint box of known general type having enteringat each end a section of a three-core cable B. The three cores B of the cable centrally Within the mg assumed that the 'terior of th are separated by spacers C in any usual fashion and each core of one section is joined to the corresponding core of the other section by ajoint which keeps a tension on the two cores. The uppermost joint is shown in section in Figure l and it, and the other two similar joints, are in tubes of insulating material D supported in the box by spacing partitions E. f

The details of the joint itself are more clearly shown in Figures 3 and 4 by reference to which figures it will be seen that the bared end of the left-hand core B is secured in a socket F screwed in the end of an outer tubular member G, whilst the end of the right-hand core B is secured in a socket H in the screwed end H of a rod H extending tube G. The inner end ofthe rod H is screwed and carries a head H and between this head and a tubular internal collar J screwed into the right-- hand end of the tube G is a strong spring K. On the screwed portion H is a nut L. Flexible metallic braiding M makes a good electrical connection between the right-hand core B? and the outer-tube G and hence to the left-hand core B.

In making the joint the spring K is first compressed by screwing the nut L against the end of the tubular collar J as indicated in Figure 5. The socket F is then screwed u into the tube G and both sockets F and 1-5 are threaded on to the adjacent ends of the cores B The ends M of the flexible braids are then placed round the right-hand core B and bound and the joint between the core, the braid and the socket H made by soldering. The socket F is then screwed back until it is flush with the end of the tube G and fixed, as for instance by running solder into the hole G The joint between the socket F and the left-hand core B is also made by soldering. The spring K is then released by slackening back the nut L as far as is desired, for instance right back to the shoulder on the socket H This places the cores in tension. The free 'ends of the flexible braids are then bent back in spiral form and bound and soldered to the outside of the tubular collar J.

The finished joint would then be as shown in Figure 3 or Figure 4. In Figure 3 the sprlng is shown as fully compressed, it becores have contracted say through a fall in, temperature. In Figure 4 the spring has expanded still keeping a tension on the cores which may be assumed to have crept or moved towards each other by expansion due to a rise in temperature.

It will be seen-that there is a small clearance space between the tube G and the ine paper or other insulating tubes D. In this space there may be a thin metal of the rod liner say of brass to form a bearing surface for the tube'G. This liner would also act to equalize electrostatic stresses on the tubes D. Such liner is not essential and is not shown in the drawings. 1f provided it would be slotted or perforated to allow thorough impregnation of the tubes D with the oil or compound with which the whole joint box is intended to be filled. The slots G in the tube G are provided to allow free access of that oil or compound to the interior of the tension joint.

It is to be understood that the details of construction are shown and described by way of example and that such details may be varied within the scope of the claims without departing from the spirit of the invention.

lVhat I claim as my invention and desire to secure by Letters Patent is l. A joint for the core of an electric cable comprising a socket to which'the core is secured and means for applying tension to said socket.

2. A joint forthe core of an electric cable comprising two sockets into which the ends of the cores to be joined are secured, and a springacting to draw the sockets towards each other and to keep the cores in tension. 3. A joint for the core of an electric cable comprising two sockets into which the ends of the cores to be joined are secured, a spring acting to draw the sockets towards each other and to keep the cores in tension, and a flexible electrical connection between the sockets.

4. A joint for the core of an electric cable comprising telescopic members, sockets attached to said members to which sockets the cores are secured, and a spring to draw the telescopic members one within the other.

5. A joint "for the core of an electric cable comprising inner and outer telescopic mem bers, sockets attached to said members to which sockets the cores are secured, a spring encircling said inner member and acting to draw it within the outer member, a screwthreaded portion on said inner member, and a nut engaging with such screwthreaded portion and cooperating with the end of the outer member so that any desired initial compression can be given to the spring before the cores are secured in the sockets. V

6. In a joint box for an electric cable, the combination of a fixed tube of insulating material, telescopic members within such tube. sockets attached to said members to which sockets the cores of the cableare secured, and a spring to draw the telescopic members one within the other. v

In testimony whereof I have signed my name to this specification. 

